GB2215270A

GB2215270A - Reinforced bitumen felts

Info

Publication number: GB2215270A
Application number: GB8804031A
Authority: GB
Inventors: Richard Russell Swift
Original assignee: TARMAC IND PRODUCTS Ltd
Current assignee: TARMAC IND PRODUCTS Ltd
Priority date: 1988-02-22
Filing date: 1988-02-22
Publication date: 1989-09-20
Also published as: GB8804031D0

Abstract

A reinforced bitumen underslating felt comprising a bitumen saturated and coated fibre base felt sheet combined with a layer of jute hessian embedded in the coating on one side of the felt so as to reinforce and strengthen the sheet, modified by the incorporation of an additional layer of non-woven plastics sheet material. The composite material of a fibre layer, a hessian layer and a non-woven plastic sheet layer completely impregnated with and encapsulated in bitumen, performs better than conventional underslating with respect to its resistance to weathering.

Description

RFINFORCFD BITUMFN FFLTS The present invention relates to reinforced bitumen felts suitahle for use as underslating.

Underslating felts have heen used extensively and successfully over the last four decades as weatherproofing under tiles or slates in pitched roof constructions. Bitumen felts (fibre base) are covered by Rritish Standard BS 747: 1977. Reinforced bitumen felts for underslating are catgegorised under Type 1F of BS 747. Type 1 felt is "a bitumen saturated and coated fibre base felt combined with a layer of jute hessian embedded in the coating on one side of the felt so as to reinforce and strengthen the sheet" (BS747). The sheet is surfaced with a surfacing material to prevent the felt sticking when stored in a roll. The presence of the hessian is obvious on inspection.This felt is also manufactuared with an aluminium foil face on the hessian reinforced side to provide a reflective insulation hessian-reinforced underslating felt.

The jute hessian reinforcement has a nominal mass per unit area of not less than 110 g/m. The nominal mass per unit area of the underslating felt is 15 kg per 1Om. The nominal mass per unit area of fibre base is 160 g/m 2 (fibre) and 110 g/m2 (hessian). T;e bitumen content of the felt is 550 gjm2 minimum. The felts are marketed in rolls 1 m wide in lengths of 15 m.

BS747 is recognised as the standard throughout the construct industry and underslating materials falling within the British Standard specification are approved for use in building construction. Any materials falling outside the composition standard of BS 747 would not automatically be considered by the construction industry as suitable for use and hence would be unlikely to be commercially successful on a large scale. Pre us attempts to completely replace RS 747 Type 1F underslating with nonstandard polymer-based sheet materials have not met with significant commercial success, partly due to the lack of British Standards approval and partly due to the tendency for these materials to be more expensve than the BS 747 Type 1F materials.

Underslating is intended to be used under the tiles or slates and is not recommended for external use. After extended exposure to water and ultra violet light, the underslating has a tendency to hecome brittle and is prone to damage. Fracturing of the material can result in the entry of moisture by capilliary action into the soffit. On a tiled or slated roof it is common that part of the underslating will he exposed in areas such as thee gutters, eaves, valleys and hips. These exposed areas of underslating are vulnerable to the elements. If the underslating of a roof fails in these areas it is generally necessary to cure the problem by removal of two or three layers of tiles/slates to facilitate replacement of the damaged underslating with new BS 747 Type 1F felt.Repair work is time-consuming and expensive; also, the need for repairs to be carried out might not be noticed until more extensive damage to roof components has occurred. Consequently, it would be advantageous to improve the performance of BS 747 Type 1F underslating so as to extend its life in this critical area.

It is now proposed to modify a standard reinforced bitumen underslating felt by incorporating in the material a strip of nonwoven plastics sheet material to improve the weathering properties at vulnerable areas such as the gutter area. The strip of sheet material could be sandwiched between the fibre and hessian layers of the felt, or could he the outer layer on one or other surface of the felt. In any case, the composite material of a fibre layer, a hessian layer and a non woven plastics sheet layer would he completely impregnated with and encapsulated in bitumen.

Various synthetic plastics materials could he used for the additional sheet layer: for example, non woven sheets of nylon, polyolefin and polypropylene are considered as suitable. However, the preferred material is a sheet of non woven spun-bonded polyester.

The properties of a typical spun-bonded polyester sheet which could be used is as follows: Weight 100 - 140 g/m2 Thickness 1-1.5 mm Tensile Strength Machine Direction 450N Transverse Direction 450N Burst Strength (Mullen) 1.400KN/m2 (Mean) Flongation of Rrake Machine Direction 405+ Transverse Direction 407+ Tear resistance (BS747 App. C) Machine Direction 200N Transverse direction 200N A preferred modified underslating felt would incorporate a 3nn mm wide strip of non woven spun-bonded polyester along one long edge of the material.This modified material would perrorm better than conventional underslating with respect to its resistance t weathering without altering its compliance with RS 747 Type ir.

The new material could he used in the repair of existing roofs -r provide new underslating in a gutter area which would be less likely to damage than the conventional underslating. The new material cou: also he used advantageously in the construction of new roofs were it could be used in all gutter areas and areas liable to exposre; the new material is, of course, compatible with the conventiona underslating which can he used in the normal manner for unders -tt.

protected areas of a roof.

Claims

1. A reinforced bitumen underslating felt comprising a bitumen saturated and coated fibre base felt sheet combined with a layer of jute hessian embedded in the coating on one side of the felt so as to reinforce and strengthen the sheet, having an additonal layer of non-woven plastics sheet material incorporated therein to provide a composite material of a fibre layer, a hessian layer and a non-woven plastics sheet layer completely impregnated with and encapsulated in bitumen.

2. A reinforced bitumen underslating felt according to claim 1, wherein the additional layer of non-woven plastics sheet material forms a strip along one edge of composite material.

3. A reinforced bitumen underslating felt according to claim 1 or 2, wherein the non-woven plastics sheet material is polyester, polyolefin or nylon.

4. A reinforced bitumen underslating felt according to claim 3, wherein the non-woven plastics sheet material is polypropylene.

5. A reinforced bitumen underslating felt according to claim 3, wherein the non-woven plastics sheet material is spun-bonded polyester.

6. A process for the production of a reinforced bitumen underslating felt according to claim 1, which comprises incorporating a layer of non-woven plastics sheet material in combination with a sheet of felt and a layer of hessian before impregnating with and encapsulating in with bitumen.

7. A reinforced bitumen underslating felt categorised under Type 1F of British Standard BS 747;77, having an additional layer of non-woven plastics sheet material incorporated therein to provide a composite material of a fibre layer, a hessian layer and a non-woven plastics sheet layer completely impregnated with and encapsulated in bitumen.